A pulse-width modulation signal (PWM) signal is often employed as a dimming control signal to regulate the brightness of a light-emitting diode (LED). In such a dimming process, duty cycle information of a PWM signal can be converted to a linear electronic signal to simulate the linear output of the LED. In one example, a first-order RC filter can be used as an LED dimming circuit. Also, the cutoff frequency (fc) of the filter can be ½πRC, where cutoff frequency fc may be less than the dimming frequency of the PWM signal. That is, the less cutoff frequency fc is, the higher the parameter R*C.